fix(ci): skip commit-subject validation in the post-merge pipeline (#41)

## Summary

Closes #40.

`main.yaml`'s `validate` job calls `ci.yaml` as a reusable workflow,
running both `Test` and `Validate Commit Subjects` post-merge. The
commit-subject check only makes sense pre-merge (should this PR be
mergeable) - by the time `main.yaml` runs, the commits are already
merged, so re-checking their subjects is meaningless. `Test` still
re-runs post-merge (verifies the actual merge result); commit-subject
validation no longer does.

Added a `skip_commit_validation` `workflow_call` input on `ci.yaml`
(default `false`, so its own `pull_request`/`workflow_dispatch` triggers
are unaffected), and `main.yaml`'s `validate` job now passes
`skip_commit_validation: true`.

## Test plan

- [x] Both edited workflow files validated with `ruby -ryaml`
- [x] Confirmed the `if: inputs.skip_commit_validation != true`
expression safely defaults to running the job for every trigger type
that doesn't explicitly pass the input (pull_request, workflow_dispatch)
- `inputs.skip_commit_validation` evaluates to `null` there, and `null
!= true` is `true`

Co-authored-by: Claude Sonnet 5 <noreply@anthropic.com>

Author: bougyman

.github/workflows/ci.yaml

@@ -4,6 +4,14 @@ name: CI
 on:  # yamllint disable-line rule:truthy
   workflow_dispatch:
   workflow_call:
+    inputs:
+      skip_commit_validation:
+        description: >-
+          Skip the commit-subject check - it only makes sense pre-merge
+          (should this PR be mergeable), not as a post-merge gate.
+        required: false
+        type: boolean
+        default: false
   pull_request:
 
 jobs:
@@ -43,6 +51,7 @@ jobs:
         run: mix test
 
   conventional_commits:
+    if: inputs.skip_commit_validation != true
     name: Validate Commit Subjects
     runs-on: ubuntu-latest
     steps:

.github/workflows/main.yaml

@@ -18,6 +18,8 @@ jobs:
   validate:
     name: Validations
     uses: ./.github/workflows/ci.yaml
+    with:
+      skip_commit_validation: true
 
   manage-release-pr:
     needs: [validate]